22,440 reputation
150116
bio website lightandmatter.com
location Fullerton, California
age
visits member for 3 years, 2 months
seen 2 hours ago

I teach physics at Fullerton College, a community college in Southern California. I have an undergrad degree in math and physics from Berkeley and a PhD in physics from Yale. Back when I was doing research, my field was experimental low-energy nuclear physics.


7h
comment What does it mean when physical theories are inconsistent?
These are really two separate questions. The second one has already been asked here: physics.stackexchange.com/q/387 I would suggest editing the question to cut the second question, since it's a duplicate.
1d
comment Undefined result of relativistic velocity addition formula
@CuriousOne: SR doesn't allow frames that move at the speed of light.
1d
comment Undefined result of relativistic velocity addition formula
@Achmed: Events don't move. Objects move.
2d
comment Does gravity slow the expansion of the universe?
The question is talking about cosmological scales.
2d
comment A universe from nothing
This doesn't address the question.
2d
comment Is a causal relationship implied by Newton's 2nd Law?
It would be pointless to discuss it in terms of concepts from 2000 years ago. See the link above for what a more modern formulation would look like. See also Earman, A primer on determinism; philsci-archive.pitt.edu/3003 ; and various other work that can be found with search terms such as "norton's dome" and "staccato run."
2d
comment Is redshift a reliable means to know how fast an object is moving away or towards an observer?
See astro.ucla.edu/~wright/stdystat.htm
2d
comment Is a causal relationship implied by Newton's 2nd Law?
Causation is hard to define, and without defining it, there's no way to answer your question. See philsci-archive.pitt.edu/1214
2d
comment How is it possible to accelerate a neutron?
By "proton-neutron atom," do you mean a deuteron?
Sep
17
comment What does the Schrodinger Equation really mean?
It's a statement of conservation of energy.
Sep
16
comment If the universe is expanding, what is it expanding into?
So if there exists a "creation point" of the universe, there is nothing beyond that just by definition. A statement of creation of the universe includes the statement that energy was indeed created at such a point. This is wrong for multiple reasons. It's wrong because general relativity doesn't even offer a way to define the total mass-energy of a cosmological spacetime. "Energy was indeed created" is also wrong. GR describes $t>0$, not $t=0$ or $t<0$. To say something was "created," you have to have a time when it didn't exist, followed by a time when it did exist.
Sep
16
comment If the universe is expanding, what is it expanding into?
When did the Big Bang happen and where did it occur? "When" we do not know. This is wrong. We know with quite good precision. It happened 13.8 billion years ago.
Sep
16
comment If the universe is expanding, what is it expanding into?
General relativity includes non-trivial topology, but it does not "predict" it in any local sense from the configuration of sources - the field can be only sometimes inconsistent with the configuration and topology. This isn't right.
Sep
16
comment If the universe is expanding, what is it expanding into?
#1 is not right. For example, if the universe has spatial curvature $\ge 0$, then a surface of constant $t$ does not have the topology of a sphere. #4. This is not a correct depiction of current knowledge.
Sep
16
comment Wormholes, time travel, and time dilation
the world line of y is curved because it depicts its journey out and back, while x is straight because it has remained stationary? Right. Even though an observer can still see x, it also exists in the past and in synchronized with y? I'm not sure what you mean by this. In relativity, talking about what observers can "see" isn't usually a good idea. Seeing works by propagation of rays of light, which happens at a finite speed.
Sep
16
comment Wormholes, time travel, and time dilation
@KevinP.Kilburn: The wormholes are created before the diagram begins. B is the point where you enter y. C is the point where you exit x. I'll edit the answer to try to clarify this.
Sep
15
comment Wormholes, time travel, and time dilation
OK. I think this agrees with the claim in Morris 1988. Does the argument in my answer seem to make sense? I'm having to fill in some of the logic that Morris didn't make explicit, so I could be wrong.
Sep
15
comment Deriving Ampère's Circuital Law from Ampère's Force Law?
There are probably many different ways to slice this kind of thing up into a set of axioms and theorems. One possible approach is given in ch. 10 of my SR book, lightandmatter.com/sr . I explicitly list four assumptions in section 10.3.1. This leads through a plausibility argument to the existence of a magnetic field and the Lorentz force law. Section 10.7 then gives a plausibility argument for Maxwell's equations. I don't claim it's a rigorous proof, but I think it shows that if you're trying to construct a reasonable theory, you end up with Maxwell's equations.
Sep
15
comment Deriving Ampère's Circuital Law from Ampère's Force Law?
For something that I think basically amounts to the converse, see physics.stackexchange.com/questions/20477/…
Sep
15
comment Wormholes, time travel, and time dilation
I've read conflicting info Please point us to your sources. E.g., authors.library.caltech.edu/6469 ?